package top.lshaci.learning.interview.lock;

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.ReentrantReadWriteLock;

/**
 * 多个线程同时读一个资源类没有问题，所以为了满足并发量，读取共享资源应该可以同时进行。但是写共享
 * 资源只能有一个线程。
 * <p>
 * 写操作：原子+独占，整个过程必须是一个完整的统一体，中间不许被分割，被打断。
 */
public class ReadWriteLockDemo {
    public static void main(String[] args) {
        MyCache myCache = new MyCache();
        for (int i = 1; i <= 5; i++) {
            final int tempInt = i;
            new Thread(() -> {
                myCache.put(tempInt + "", tempInt + "");
            }, String.valueOf(i)).start();
        }

        for (int i = 1; i <= 5; i++) {
            final int tempInt = i;
            new Thread(() -> {
                myCache.get(tempInt + "");
            }, String.valueOf(i)).start();
        }
    }

    static class MyCache {
        private volatile Map<String, Object> map = new HashMap<>();
        //    private Lock lock = new ReentrantLock();
        private ReentrantReadWriteLock reentrantReadWriteLock = new ReentrantReadWriteLock();

        public void put(String key, Object value) {

            reentrantReadWriteLock.writeLock().lock();
            try {
                System.out.println(Thread.currentThread().getName() + "\t 正在写入：" + key);
                try {
                    TimeUnit.MILLISECONDS.sleep(300);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                map.put(key, value);
                System.out.println(Thread.currentThread().getName() + "\t 写入完成");
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                reentrantReadWriteLock.writeLock().unlock();
            }

        }

        public void get(String key) {
            reentrantReadWriteLock.readLock().lock();
            try {
                System.out.println(Thread.currentThread().getName() + "\t 正在读取：" + key);
                try {
                    TimeUnit.MILLISECONDS.sleep(300);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                Object result = map.get(key);
                System.out.println(Thread.currentThread().getName() + "\t 读取完成" + result);
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                reentrantReadWriteLock.readLock().unlock();
            }

        }

    }
}
